Construction Of Perovskite Solar Cells And Optimization Of Their Components,Microstructures And Performances

Since the first report in 2009,perovskite solar cells(PSCs)have attracted extensive attention of the researchers due to their excellent optoelectronic properties,simple preparation procedure and unprecedented growth rate of power conversion efficiency(PCE).However,the most commonly used mesoporous-structure devices still have some shortcomings,such as multi-step fabrication,complex interface and high-cost materials,which are detrimental to large-scale manufacture.Therefore,selection and optimization of device structure and the component materials(like hole/electron-transporting materials and light-absorbing perovskite materials)is one of the research focuses.Thus,we carried out the investigation on the key component materials and constructed PSCs with different structures respectively.The performance and practical application potential of devices were enhanced by developing new materials and optimizing the preparation technique.The main research contents and conclusions are as follows:1.Low-cost symmetrically tert-butyl substituted zinc phthalocyanine(ZnPc(tBu)4)synthesized through a one-step route,is used as a new type hole-transporting material(HTM)for PSCs.ZnPc(tBu)4 HTM layer is fabricated through solution spin-coating process,that lowers equipment requirements and is more conductive to the development of industrialization.Spectroscopic and Cyclic voltammogram measurements are employed to determined energy band level position of ZnPc(tBu)4,showing ZnPc(tBu)4 has higher HOMO value than the valence band level of perovskite in favor of directionally transportation of holes.Combined with anatase TiO2 nanoparticles as electron-transporting layer and CH3NH3PbI3(MAPbI3)as light absorption active layer,mesoporous structure PSCs are constructed.When the concentration of dopant-free ZnPc(tBu)4 is 10 Mm,the best performing ZnPc(tBu)4-based PSC achieves a PCE of 5.16%.This ZnPc(tBu)4 HTM exhibits wide application potential in PSCs with advantages such as simple synthesis,low-cost,easy fabrication of film,high hole mobility and chemical stability,and provides a new idea for the development of new type HTMs.2.To develop high performance electron-transporting materials(ETMs)with ordered structures,rutile Ti02 array films with different morphologies are synthesized on FTO,and the effects of their nanostructures on device performance are investigated.1)Using TiCl3 as a titanium source,the morphology and thickness of TiO2 array are controlled by changing the duration time of low-temperature(70 ℃)chemical bath deposition.A closely aligned nanoneedles/nanosheets array with best charge separation efficiency and hole-blocking ability is obtained at 60 min,and the corresponding CH3NH3Pbl3-based PSC achieves a PCE up to 15.4%,which can be improved to 18.4%by using the more efficient perovskite of(FA0.83MA0.17)0.95Cs0.05Pb(I0.9Br0.1)3.This work provides a new effective ETM for PSCs.2)Using TBOT as titanium source,rutile TiO2 nanorod array is synthesized by one-step hydrothermal method,and turned to hierarchical structure array via a second reaction.The hierarchical TiO2 nanorod array can improve the interface contact and the efficiency of charge separation,which reduce electrons recombination and achieve better device performance than nanorod array.This work provides a reference for the preparation,morphology regulation and application in PSCs of ordered nanoscale semiconductor arrays.3.Symmetrically tert-butyl substituted copper phthalocyanine(CuPc(tBu)4)with suitable energy band position and excellent hole conductivity is employed as HTM for PSCs.Accompanied with above-mentioned mixed nanoneedles/nanosheets rutile TiO2 array film as ETM,(FA0.83MA0.17)0.95Cs0.05Pb(I0.9Br0.1)3 as light absorption active layer,low-cost and high efficient PSCs are constructed.The effects of CuPc(tBu)4 concentration on the performance of PSCs are investigated.The aggregation degree of CuPc(tBu)4 HTM layer increase with the rise of CuPc(tBu)4 concentration,and correspondingly the PCE of devices first increase and then decrease.When the concentration is too high,CuPc(tBu)4 aggregate into particles and form inhomogeneous films,which is bad for interface contact and charge separation,and then resulting in aggravated charge recombination and reduced PCE.As the concentration of dopant-free CuPc(tBu)4 is 10 mg mL-1,the optimal device efficiency(13.7%)is achieved,comparable with the PCE(13.9%)of dopant-free spiro-OMeTAD based PSCs.Al2O3 as buffer layer is introduce to improve the interface contact and avoid the direct contact between Au electrode and perovskite,and increases PCE to 14.8%.This work has a certain reference value for the structure design,materials selection and optimization of PSCs.4.For the improvement of the quality of perovskite(MAPbI3-xClx)films prepared by one-step solution process and the performance of the planar heterojunction device based on TiO2 blocking layer,CuPc(tBu)4 is used as MAPbI3-xClx precursor additive for the first time,and its effects on perovskite film quality and device performance are studied.Trace CuPc(tBu)4 additive play as nucleation sites to promote the formation of continuous perovskite layer with enhanced crystallinity and surface coverage.High quality MAPbI3.xClx films with lower defect state density can facilitate light absorption and reduce charge recombination,then improve the Jsc and PCE of PSCs.The best device efficiency increases from 15.3%to 17.3%by using 4.4 ×10-3 mM of CuPc(tBu)4 in the precursor solution.This work widens the application range of metal phthalocyanine in PSCs,and paves a new way for the preparation of high quality perovskite films and high performance planar heterojunction PSCs.